Implantation of ni nano domains in refractory metal oxide support by means of sol-gel encapsulation - an effective solution to coke formation in the partial oxidation of natural gas

ABSTRACT

A metal oxide-supported nickel catalyst includes a matrix containing a metal oxide and catalytic sites distributed throughout the matrix and having an intricate interface with the matrix, in which the catalytic sites are selected from the group consisting of nano-nickel(0) domains and nano-nickel(0)-A(0) alloy domains. Also disclosed are a method for preparing this catalyst and a method for using it to produce carbon monoxide and hydrogen by partial oxidation of a C 1 -C 5  hydrocarbon.

BACKGROUND OF THE INVENTION

Catalytic partial oxidation (or dry reforming) of methane (POM), otherlight alkane compounds existing in natural gas (e.g., C₂-C₅ alkanes),and alcohols producing synthesis gas (CO+2H₂) can be integrated as ananodic reaction (CH₄+O²⁻→CO+2H₂+2e⁻) with the electrochemical separationof air (½O₂+2e⁻→O²⁻), a cathodic reaction, to form a catalytic membranereactor. This combination has paramount commercial value in terms ofsaving energy and production of H₂, N₂, and a series of useful chemicalintermediates. Currently, the obstacle to the industrial reforming oflight hydrocarbon gases is still deactivation of metal oxide-supportedNi(0) catalyst due to deposition of carbon on Ni(0) catalytic sites.

This invention provides a solution to this dilemma through developing anew synthetic route for preparing a catalyst.

SUMMARY OF THE INVENTION

In one aspect, the invention features a metal oxide-supported nickelcatalyst including a matrix containing a metal oxide and catalytic sitesdistributed throughout the matrix and having an intricate interface withthe matrix, in which the metal oxide can be Al₂O₃, SiO₂, CaO, MgO, ZrO₂,CeO₂, TiO₂, or Y₂O₃ (e.g, Al₂O₃, SiO₂, CaO, or ZrO₂); and the catalyticsites can be nano-nickel(0) domains or nano-nickel(0)-A(0) alloydomains, A being Rh, Pd, Pt, Ru, Cu, or Co (e.g, Rh), providing thatwhen the catalytic sites are nano-nickel(0)-A(0) alloy domains,nickel(0) constitutes at least 95 wt % in the alloy domains. Based onthe total weight of the catalyst, the weight percentage of the metaloxide-containing matrix is 70-85% and the weight percentage of thecatalytic sites is 15-30% (e.g., 18-22 wt %).

Each of these catalytic sites has an intricate (i.e., complexinterpenetrating) interface with the matrix. In other words, there is noclear-cut interfacial boundary between the catalytic site and thematrix. The particular interface results from amalgamation between thecatalytic site and the matrix at their interfacial boundary.

In another aspect, this invention features a method of preparing ametal-oxide supported nickel catalyst. The method includes at least fivesteps: (i) producing in an aqueous medium (Ni_(x)O_(y))(OH)_(2(x−y))particles and, optionally, another metal-containing particles selectedfrom the group consisting of (A_(n)O_(m))(OH)_(3(n−2/3m)) particles and(A_(n)O_(m))(OH)_(2(n−m)) particles, thus forming a colloidalsuspension, in which 1≦x≦100, y<x, 1≦n≦100, m<n, A is a metal selectedfrom the group consisting of Rh, Pd, Pt, Ru, Cu, and Co, and theparticles are stabilized by a surfactant; (ii) adding a compound offormula M_(p)(OR)_(q) to the colloidal suspension to form a sol, inwhich p is 1; q can be 2, 3, or 4; M can be Al, Si, Ca, Mg, Zr, Ce, Ti,or Y; and R can be H or C_(g)H_(2g+1), g being an integer between 1 and4; (iii) heating the sol at an adequate temperature (e.g., 60-100° C.)to form a gel; (iv) calcining the gel at a temperature just high enough(e.g., 580-620° C.) to burn out organic components to form a metaloxide-supported nickel oxide catalyst, which contains NiO and,optionally, A_(n)O_(m); and (v) reducing the metal oxide-supportednickel oxide catalyst to form a metal oxide-supported nickel catalystcontaining catalytic sites that are selected from the group consistingof nano-nickel(0) domains and nano-nickel(0)-A(0) alloy domains,respectively. The reducing step can be performed in hydrogen or methane.

The (Ni_(x)O_(y))(OH)_(2(x−y)) particles, (A_(n)O_(m))(OH)_(3(n−2/3m))particles, and (A_(n)O_(m))(OH)_(2(n−m)) particles can be stabilizedusing any surfactant that leads to a stable oil-in-water emulsion. Inparticular, one can use a surfactant or a blend of surfactants that hasa hydrophile-lipophile balance value of 8-16. For example, one can usen-hexadecyl trimethyl ammonium bromide.

The metal oxide-supported nickel catalyst prepared by theabove-described method is also within the scope of this invention.

In still another aspect, this invention features a method of producingcarbon monoxide and hydrogen by partial oxidation of a C₁-C₅hydrocarbon. In this method, a gaseous stream containing a C₁-C₅hydrocarbon and oxygen gas is fed into a reactor, in which theabove-described metal-oxide supported nickel catalyst is placed toproduce carbon monoxide and hydrogen at 700-900° C. The metal-oxidesupported nickel catalyst used in this method, as mentioned above,contains catalytic sites that can be nano-nickel(0) domains ornano-nickel(0)-A(0) alloy domains and have a particular interface withthe matrix. This interface can effectively prevent the Ni domains frommerging at a typical catalytic dry reforming temperature (800-900° C.).As a result, the catalyst becomes highly immune to coking. For example,it can retain a high methane conversion (X_(CH4)>90%) and syngasselectivity (S_(CO)>85%) over a long run (e.g., 6 hours) of partialoxidation of methane.

The details of one or more embodiments of the invention are set forth inthe description below. Other features, objects, and advantages of theinvention will be apparent from the following drawings, detaileddescription of several embodiments, and also from the appending claims.

DETAILED DESCRIPTION

This invention is based in part on an unexpected discovery that acertain preparation method leads to a metal oxide-supported Ni catalystthat retains high methane conversion (X_(CH4)>90%) and syngasselectivity (S_(CO)>85%) over a long run of partial oxidation ofmethane.

Syngas is a significant industrial gas mixture having applications inhydrogen, methanol, acetic acid production, and Fischer-Tropsch (FT)synthesis to prepare synfuel. Syngas is commercially produced by steamreforming of natural gas (CH₄+H₂O→CO+3H₂) at high temperature (850°C.-1000° C.) under pressure (10-40 atm) in the presence of a group VIIImetal (e.g., Rh, Ru, Pt, Ir, Pd, Ni) catalyst. However, it is a highlyendothermic process. On the contrary, the catalytic partial oxidation ofmethane (POM) to syngas is a mild exothermic process (−35.7 kJ.mol⁻¹),it has therefore been extensively studied for many years(CH₄+½O₂→CO+2H₂). Compared with the conventional steam reformingprocess, the partial oxidation has the advantages of slight heatrelease, low pressure, and smaller reactors.

Supported nickel catalysts, particularly nickel supported on refractorymaterials (e.g., Al₂O₃, SiO₂, ZrO₂, CeO₂, TiO₂, MgO, CaO, La₂O₃, Y₂O₃,HfO₂, Si₃N₄, Sm₂O₃), have been developed for carrying out POM. To date,the catalytic partial oxidation of light hydrocarbon gases has not yetbeen operated in industrial scale due to a lack of qualified catalysts.An industrially competitive reforming catalyst must be economic, displaya high feedstock conversion and a high selectivity to syngas, and assurestable performance over the designated operation period of time. Themajor advantages of a Ni catalyst system are a low cost and, in general,a high activity and selectivity. However, they suffer from poorstability, which is the result of the sintering of fine Ni metalparticles and coke formation (carbon deposition) on Ni sites atreforming temperature (800-900° C.).

Extensive work has, therefore, been carried out to improve the stabilityof the nickel catalyst system. It has been comprehended that cokeformation can be significantly alleviated by reducing Ni crystallites;however, the decrease in active nickel particle sizes weakens theirresistance to sintering. Hence, to achieve a high performance-basedcatalytic stability, the desired catalyst structure must be able toinhibit both coke formation and sintering coincidentally. In the lastdecade, efforts towards this goal produced three representativeadvancements as highlighted below.

Ruckenstein et al. (“Methane Partial Oxidation Over NiO/MgO SolidSolution Catalysts,” Appl. Catal. A 183:85-92 (1999)) disclosed theNiO/MgO solid solution catalysts for partial oxidation of methane tosynthesis gas at high space velocity. The NiO (35 mol %)/MgO catalystshowed good stability at 850° C. for 50 hours; however, the activity andstability of the NiO/MgO catalyst are sensitive to the NiOconcentration, i.e. a departure from this solid solution compositionwill cause elapsing of the original advantage.

Takenaka et al. (“Specific Performance of Silica-coated Ni Catalysts forthe Partial Oxidation of Methane to Synthesis Gas,” J. Catalysis245:392-400 (2007)) disclosed the water-in-oil micro-emulsion method forpreparing nano-sized nickel metal particles (5 nm) covered by 10 nmsilica layers. This catalyst fabrication process indeed brings about agreater improvement on the catalytic stability of the supported Nicatalyst than conventional impregnation method. However, by this means,the active nickel concentration in the catalyst is low (<5 wt %). Withsuch a low loading level of catalytic component, a high temperature(˜850° C.) becomes necessary to achieve a high feedstock conversion andsyngas selectivity. Nevertheless, at the high reforming temperatures,the Ni loading level should be high enough (>10 wt %) to tolerate theevaporation of nickel species in order to maintain a stable output ofPOM over a long run.

Incorporation of precious metals, such as Rh and Pt, into the supportedNi catalysts is an other effective measure to revamp the supported Nireforming catalyst system [Choudhary et al. “Beneficial Effects of NobleMetal Addition to Ni/Al₂O₃ Catalyst for Oxidative Methane-to-SyngasConversion,” J. Catalysis 157 (1995) 752-754]. Yet, this approachobviously increases material cost.

In conclusion, as far as the supported Ni catalyst is concerned, it isstill a considerably challenging task to maintain a high conversion rateof reactant gas and high selectivity for CO and H₂ for even a pilot run.None of the existing supported nickel catalysts has claimed such traitdue to the aforementioned dilemmas.

This invention has explored a new chemical preparation approach thatlays down a unique microstructure of the active Ni site in the commonlyadopted refractory oxide support. As a result, the catalyst presents asteady high activity and selectivity in POM over a long reaction periodof time (e.g., 300 hours). By this approach, (Ni_(x)O_(y))(OH)_(2(x−y))sol particles and, optionally, another metal-containing sol particlesselected from the group consisting of (A_(n)O_(m))(OH)_(3(n−2/3m))particles and (A_(n)O_(m))(OH)_(2(n−m)) particles, A being Rh, Pd, Pt,Ru, Cu, or Co, are stabilized by a suitable surfactant upon theirgeneration in an aqueous medium. Then, these sol particles are dispersedin a large excess of a sol dispersion of a metal hydroxide (R=H) ormetal organoxide (R=C_(g)H_(2g+1), g=1-4) [M_(p)(OR)_(q)], where themetal M represents a metal ion of a refractory support (e.g., Al₂O₃,SiO₂, CaO, MgO, ZrO₂, CeO₂, TiO₂, or Y₂O₃). The sol particles generatedfrom M_(p)(OR)_(q) are then subjected to gellation, whilst thesurfactant-encapsulated (Ni_(x)O_(y))(OH)_(2(x−y)) sol particles (and,optionally, another metal-containing sol particles described above) areembedded in-situ in the M_(p)O_(q) gel formed. After that, the resultant(Ni_(x)O_(y))(OH)_(2(x−y)) sol (and, optionally, anothermetal-containing sol particles)/M_(p)O_(q) gel system is calcined in airto form a metal oxide supported nickel oxide catalyst, and consecutivelyreduced in H₂ to generate the desired supported Ni catalyst. Theconfinement role of the M_(p)O_(q) gel prevents congregation of nickelcrystallites and hence effectively inhibits deposition of coke asmanifested by an electron micrographic study.

Of note, as shown in the example below, the metal oxide supported nickeloxide catalyst can also be reduced in CH₄ (NiO+nCH₄→Ni(C_(n))+xH₂+yH₂O,x>>y) at a reaction temperature which normally falls in the range of700-950° C. In this temperature range, methane will undergo combustionat the same time since its auto ignition temperature is about 600° C.The carbon dioxide and steam produced from the combustion(CH₄+2O₂→CO₂+2H₂O), will further clean up the carbon filaments formed onNi through the reactions, CO₂+C→2CO and 2H₂O+C→CO₂+2H₂.

In addition, it is important to note that the method of this inventionand the conventional impregnation method result in two completelydifferent chemical microenvironments even though Ni crystallites areseated on the same support (e.g., ZrO₂) with the same Ni loading level(e.g., 20 wt %), as evidenced by temperature-programmed reduction (TPR)experiments. TPR of the catalyst of this invention shows two equivalentreduction peaks at 700° C. and 880° C., while the catalyst obtained bythe impregnation method shows a reduction peak at 420° C. with twoshoulder peaks at 500° C. and 550° C. For TPR diagrams, thehigh-temperature peak results from reduction of NiO located at theinterfacial area. The catalyst of this invention shows that a very hightemperature (˜880° C.) is required to drive the reduction of interfacialNiO species. In addition, compared with the bulk-reduction peak at 700°C., a comparable peak area for the reduction of interfacial species isdisplayed, meaning that a significant amount of these species arepresent in the sample.

In principle, the H₂-reduction temperature unveils information aboutchemical microenvironments where Ni crystallites are located. A higherreduction temperature is usually required in order to reduce NiO domainsthat are smaller in size and intermingle to a higher extent with thematrix of support. As a result, smaller and more dispersively embeddedNi crystallites are produced after reduction. The NiO-metal oxidecatalyst of this invention provides a highly diffusive interface betweeneach NiO domain and the matrix so that reduction of NiO domains requiresmuch higher TPR temperatures than those NiO prepared by thermaldecomposition of Ni(NO₃)₂ on ZrO₂.

Furthermore, the TPR-based explanation of microstructures can beverified by Transmission Electron Microscopy (TEM), which should showNi(0) particles in contrast to ZrO₂ support on TEM image providing Ni(0)particles have a clear-cut boundary between them and the support. TheTEM images demonstrate that, for a non-trivial (i.e., 20 wt %) Niloading, Ni(0) particles cannot be distinguished from the matrix by TEM,an indication that Ni(0) particles are miniature and own a mutualpenetrating interface with the matrix.

Without further elaboration, it is believed that the above descriptionhas adequately enabled the present invention. The following examplesare, therefore, to be construed as merely illustrative, and notlimitative of the remainder of the disclosure in any way whatsoever. Allof the publications cited herein are hereby incorporated by reference intheir entirety.

Example 1 Preparation of Al₂O₃-Supported Ni Catalyst

15.0 g Ni(NO₃)₂.6H₂O and 5.0 g n-hexadecyl trimethylammonium bromide(CTAB) were dissolved in 100 ml water at 65° C. with stirring, and thenafter the solution was cooled down to room temperature 10 mltetramethylammonium hydroxide (TMAH, 1.0 M aqueous solution) was addedinto it with immediate blending. A stable (Ni_(x)O_(y))(OH)_(2(x−y))colloidal suspension was formed after the above mixture was stirred forabout 1 hour. This was followed by the introduction of 60 g aluminumisopropoxide into the resulting (Ni_(x)O_(y))(OH)_(2(x−y)) colloidalsuspension at room temperature, and the suspension formed wasball-milled using ceramic media for 72 hours, which led to a homogeneoussol dispersion. This sol-dispersion was thickened at 80° C. to form asolid gel, and the solid gel was finally subjected to calcination at600° C. for 4 hours to generate an Al₂O₃-supported Ni catalyst with 22wt % nickel loading.

Example 2 Preparation of SiO₂-Supported Ni Catalyst

15.0 g Ni(NO₃)₂.6H₂O and 5.0 g CTAB were dissolved in 100 ml water at65° C. with stirring, and after the solution was cooled down to roomtemperature 10 ml TMAH (1.0M aqueous solution) was added into it withimmediate blending. A stable (Ni_(x)O_(y)(OH)_(2(x−y)) colloidalsuspension was formed after the above mixture was stirred for about 1hour. This was followed by the introduction of 60 ml tetraethylorthosilicate (TEOS) into the resulting (Ni_(x)O_(y)(OH)_(2(x−y))colloidal suspension at room temperature. The mixture was homogenized bystirring overnight at room temperature and then the stirring wascontinued at 65° C. for additional 24 h to allow complete hydrolysis ofTEOS to form a sol suspension. This sol-dispersion was converted to asolid gel after being thickened at 80° C., and the solid gel was finallysubjected to calcination at 600° C. for 4 hours to generate aSiO₂-supported Ni catalyst with 18 wt % nickel loading.

Example 3 Preparation of CaO-Supported Ni Catalyst

15.0 g Ni(NO₃)₂.H₂O and 5.0 g CTAB were dissolved in 100 ml water at 65°C. with stirring, and then after the solution was cooled down to roomtemperature 10 ml TMAH (1.0 M aqueous solution) was added into it withimmediate blending. A stable (Ni_(x)O_(y))(OH)_(2(x−y)) colloidalsuspension was formed after the above mixture was stirred for about 1hour. This was followed by addition of 12 g CaO into the resulting(Ni_(x)O_(y))(OH)_(2(x−y)) colloidal suspension at room temperature, andthe suspension was ball-milled using ceramic for 72 hours. In thisprocess, the surface of CaO becomes a hydrogel layer comprising Ca(OH)₂species in the basic medium. Therefore, (Ni_(x)O_(y))(OH)_(2(x−y)) solparticles can effectively enter in this hydrogel layer. The suspensionwas thickened at 80° C. to form a solid gel and the solid gel wasfinally subjected to calcination at 600° C. for 4 hours to generate aCaO-supported Ni catalyst with 22 wt % nickel loading.

Example 4 Preparation of 20 wt % Ni—ZrO₂ Catalyst

15.0 g Ni(NO₃)₂.6H₂O and 5.0 g CTAB were dissolved in 100 ml water at65° C. with stirring, and then after the solution was cooled down toroom temperature 10 ml TMAH (1.0 M aqueous solution) was added into itwith immediate blending. A stable (Ni_(x)O_(y))(OH)_(2(x−y)) colloidalsuspension was formed after the above mixture was stirred for about 1hour. This was followed by the introduction of 47 g zirconium (IV)butoxide (80 wt % solution in 1-butanol) into the resulting(Ni_(x)O_(y))(OH)_(2(x−y)) colloidal suspension at room temperature, andthe suspension generated was stirred overnight to complete hydrolysis,which led to a homogeneous sol dispersion. This sol-dispersion wasthickened at 80° C. to form a solid gel, and the solid gel was finallysubjected to calcination at 600° C. for 4 hours to generate aZrO₂-supported Ni catalyst with 20 wt % nickel loading.

Comparative Example Preparation of 20 wt % Ni—ZrO₂ Catalyst byImpregnation Method

A fine ZrO₂ powder was made by hydrolysis of zirconium (IV) butoxide inwater and followed by calcination at 600° C. for 4 hours. The ZrO₂powder obtained had an average particle diameter of about 300 nm and aBET surface area of 10.2 m²/g. Thereafter, 1.6 g ZrO₂ was introducedinto an aqueous solution consisting of 1.98 g Ni(NO₃)₂.6H₂O and 50 mlwater. The resulting suspension was dried and calcined at 600° C. for 4hours to form a ZrO₂-supported Ni catalyst with 20 wt % nickel loading.

Example 5 Assessment of the Supported Ni Catalysts in POM

The catalysts obtained from the above preparation procedures wereevaluated for partial oxidation of methane at 850° C. For example, forthe Al₂O₃-Ni catalyst, the reactant stream comprised four components:He/N₂/CH₄/O₂ (with a molar ratio of 37.3/3.8/2/1), and gas hourly spacevelocity (GHSV) was 245,195 h⁻¹. After time-on-stream of 6 hours,methane conversion was higher than 95%, CO selectivity was higher than98%, and the H₂/CO molar ratio was 2/1.

TABLE 1 A comparison of the POM performance of different catalyststime-on- X_(CH4) S_(CO) Catalyst stream GHSV (h⁻¹) (mol %) (mol %) H₂/COAl₂O₃-Ni* 6 245,195 95 98 2 SiO₂-Ni* 3 68,120 98 97 2 CaO-Ni* 7 90,64098.6 94 2 ZrO₂-Ni** 20 125,200 98.9 99.9 2 He/N₂/CH₄/O₂: *molar ratio of37.3/3.8/2/1; **molar ratio of 56/3.8/3/1.

Example 6 Testing the Catalytic Stability of the ZrO₂—Ni Catalyst in POM

After being used to catalyze POM (as listed in Table 1), the ZrO₂—Nicatalyst was reused in a new round, in which the molar ratio of reactantgas mixture He/N₂/CH₄/O₂ was 37.3/3.8/2/1 and the GHSV was 125,200 h⁻¹.The catalyst displayed steadily very high activity (X_(CH4)>95%) andselectivity of POM (S_(CO)>95%) over 300 hours.

Example 7 Preparation of ZrO₂ Supported Ni(Rh) Catalyst

15.0 g Ni(NO₃)₂.6H₂O, 0.40 g RhCl₃.xH₂O and 5.1 g CTAB are dissolved in100 ml water at 65° C. with stirring, and then after the solution iscooled down to room temperature 10.5 ml TMAH (1.0 M aqueous solution) isadded into it with immediate blending. A stable colloidal suspensioncomprising (Ni_(x)O_(y))(OH)_(2(x−y)) and (Rh_(n)O_(m))(OH)_(3(n−2/3m))sol particles is formed after the above mixture is stirred for about 1hour. This is followed by the introduction of 47 g zirconium (IV)butoxide (80 wt % solution in 1-butanol) into the resulting colloidalsuspension at room temperature, and the suspension generated is stirredovernight to complete hydrolysis, which leads to a homogeneous soldispersion. This sol-dispersion is thickened at 80° C. to form a solidgel, and the solid gel is finally subjected to calcination at 600° C.for 4 hours to generate a ZrO₂-supported Ni (97.08 mol %)-Rh (2.92 mol%) catalyst with 20 wt. % Ni—Rh alloy loading.

Example 8 Preparation of ZrO₂ Supported Ni(Pd) Catalyst

15.0 g Ni(NO₃)₂.6H₂O, 3 mL Pd(NO₃)₂ solution (10 wt %, d=1.118 g/mL) and5.1 g CTAB are dissolved in 100 ml water at 65° C. with stirring, andthen after the solution is cooled down to room temperature 10.5 ml TMAH(1.0 M aqueous solution) is added into it with immediate blending. Astable colloidal suspension comprising (Ni_(x)O_(y))(OH)_(2(x−y)) and(Pd_(n)O_(m))(OH)_(2(n−m)) sol particles is formed after the abovemixture was stirred for about 1 hour. This is followed by theintroduction of 47 g zirconium (IV) butoxide (80 wt % solution in1-butanol) into the resulting colloidal suspension at room temperature,and the suspension generated is stirred overnight to completehydrolysis, which leads to a homogeneous sol dispersion. Thissol-dispersion is thickened at 80° C. to form a solid gel, and the solidgel is finally subjected to calcination at 600° C. for 4 hours togenerate a ZrO₂-supported Ni (97.26 mol %)-Pd (2.74 mol %) catalyst with20 wt. % Ni—Pd alloy loading.

Other Embodiments

All of the features disclosed in this specification may be combined inany combination. Each feature disclosed in this specification may bereplaced by an alternative feature serving the same, equivalent, orsimilar purpose. Thus, unless expressly stated otherwise, each featuredisclosed is only an example of a generic series of equivalent orsimilar features.

From the above description, one skilled in the art can easily ascertainthe essential characteristics of the present invention, and withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various usages andconditions. Thus, other embodiments are also within the scope of thefollowing claims.

1. A metal oxide-supported nickel catalyst comprising a matrix, 70-85 wt%, containing a metal oxide, and catalytic sites, 15-30 wt %,distributed throughout the matrix and having an intricate interface withthe matrix, wherein the metal oxide is selected from the groupconsisting of Al₂O₃, SiO₂, CaO, MgO, ZrO₂, CeO₂, TiO₂, and Y₂O₃; and thecatalytic sites are selected from the group consisting of nano-nickel(0)domains and nano-nickel(0)-A(0) alloy domains, A being Rh, Pd, Pt, Ru,Cu, or Co, providing that when the catalytic sites arenano-nickel(0)-A(0) alloy domains, nickel(0) constitutes at least 95 wt% in the alloy domains.
 2. The catalyst of claim 1, wherein thecatalytic sites are nano-nickel(0) domains.
 3. The catalyst of claim 2,wherein the metal oxide is Al₂O₃, SiO₂, CaO, or ZrO₂.
 4. The catalyst ofclaim 3, wherein the catalytic sites constitute 18-22 wt % of thecatalyst.
 5. The catalyst of claim 1, wherein the catalytic sites arenano-nickel(0)-A(0) alloy domains.
 6. The catalyst of claim 5, wherein Ais Rh.
 7. The catalyst of claim 5, wherein the metal oxide is Al₂O₃,SiO₂, CaO, or ZrO₂.
 8. The catalyst of claim 7, wherein the catalyticsites constitute 18-22 wt % of the catalyst.
 9. The catalyst of claim 8,wherein A is Rh.
 10. A method for preparing a metal oxide-supportednickel catalyst, the method comprising producing in an aqueous medium(Ni_(x)O_(y))(OH)_(2(x−y)) particles and, optionally, anothermetal-containing particles selected from the group consisting of(A_(n)O_(m))(OH)_(3(n−2/3m)) particles and (A_(n)O_(m))(OH)_(2(n−m))particles, thus forming a colloidal suspension, wherein 1≦x≦100, y<x,1≦n≦100, m<n, A is a metal selected from the group consisting of Rh, Pd,Pt, Ru, Cu, and Co, and the particles are stabilized by a surfactant;adding a compound of formula M_(p)(OR)_(q) to the colloidal suspensionto form a sol, wherein p is 1; q is 2, 3, or 4; M is a metal selectedfrom the group consisting of Al, Si, Ca, Mg, Zr, Ce, Ti, and Y; and R isH or C_(g)H_(2g+1), g being an integer between 1 and 4; heating the solto form a gel; calcining the gel to form a metal oxide-supported nickeloxide catalyst; and reducing the metal oxide-supported nickel oxidecatalyst to form a metal oxide-supported nickel catalyst containingcatalytic sites that are selected from the group consisting ofnano-nickel(0) domains and nano-nickel(0)-A(0) alloy domains.
 11. Themethod of claim 10, wherein in the reducing step the metaloxide-supported nickel oxide catalyst is reduced by H₂.
 12. The methodof claim 10, wherein in the reducing step the metal oxide-supportednickel oxide catalyst is reduced by CH₄.
 13. The method of claim 10,wherein the heating step is performed at 60-100° C.
 14. The method ofclaim 10, wherein the calcining step is performed at 580-620° C.
 15. Themethod of claim 10, wherein the surfactant has a hydrophile-lipophilebalance value of 8-16.
 16. The method of claim 15, wherein thesurfactant is n-hexadecyl trimethylammonium bromide.
 17. A metaloxide-supported nickel catalyst prepared by a method comprising:producing in an aqueous medium (Ni_(x)O_(y))(OH)_(2(x−y)) particles and,optionally, another metal-containing particles selected from the groupconsisting of (A_(n)O_(m))(OH)_(3(n−2/3m)) and (A_(n)O_(m))(OH)_(2(n−m))particles, thus forming a colloidal suspension, wherein 1≦x≦100, y<x,1≦n≦100, m<n, A is a metal selected from the group consisting of Rh, Pd,Pt, Ru, Cu, and Co, and the particles are stabilized by a surfactant;adding a compound of formula M_(p)(OR)_(q) to the colloidal suspensionto form a sol, wherein p is 1; q is 2, 3, or 4; M is a metal selectedfrom the group consisting of Al, Si, Ca, Mg, Zr, Ce, Ti, and Y; and R isH or C_(g)H_(2g+1), g being an integer between 1 and 4; heating the solto form a gel; calcining the gel to form a metal oxide-supported nickeloxide catalyst; and reducing the metal oxide-supported nickel oxidecatalyst to form a metal oxide-supported nickel catalyst; wherein themetal oxide-supported nickel catalyst contains a matrix, 70-85 wt %,including a metal oxide; and catalytic sites, 15-30 wt %, distributedthroughout the matrix and having an intricate interface with the matrix,in which the metal oxide is selected from the group consisting of Al₂O₃,SiO₂, CaO, MgO, ZrO₂, CeO₂, TiO₂, and Y₂O₃; and the catalytic sites areselected from the group consisting of nano-nickel(0) domains andnano-nickel(0)-A(0) alloy domains, A being Rh, Pd, Pt, Ru, Cu, or Co,providing that when the catalytic sites are nano-nickel(0)-A(0) alloydomains, nickel(0) is at least 95 wt % in the alloy domains.
 18. Thecatalyst of claim 17, wherein in the producing step only(Ni_(x)O_(y))(OH)_(2(x−y)) particles are produced so as to form a metaloxide-supported nano-nickel(0) domains catalyst.
 19. The catalyst ofclaim 18, wherein the metal oxide is Al₂O₃, SiO₂, CaO, or ZrO₂.
 20. Thecatalyst of claim 19, wherein the catalytic sites constitute 18-22 wt %of the catalyst.
 21. The catalyst of claim 17, wherein in the producingstep both (Ni_(x)O_(y))(OH)_(2(x−y)) particles and anothermetal-containing particles are produced so as to form a metaloxide-supported nano-nickel(0)-A(0) alloy domains catalyst is formed.22. The catalyst of claim 21, wherein A is Rh.
 23. The catalyst of claim21, wherein the metal oxide is Al₂O₃, SiO₂, CaO, or ZrO₂.
 24. Thecatalyst of claim 23, wherein the catalytic sites constitute 18-22 wt %of the catalyst.
 25. The catalyst of claim 24, wherein A is Rh.
 26. Amethod for producing carbon monoxide and hydrogen by partial oxidationof a C₁-C₅ hydrocarbon, the method comprising placing in a reactor ametal oxide-supported nickel catalyst of claim 1, and feeding into thereactor a gaseous stream containing a C₁-C₅ hydrocarbon and oxygen gasto allow the C₁-C₅ hydrocarbon to react with oxygen gas at 700-900° C.to produce carbon monoxide and hydrogen.
 27. A method for producingcarbon monoxide and hydrogen by partial oxidation of a C₁-C₅hydrocarbon, the method comprising placing in a reactor a metaloxide-supported nickel catalyst of claim 17, and feeding into thereactor a gaseous stream containing a C₁-C₅ hydrocarbon and oxygen gasto allow the C₁-C₅ hydrocarbon to react with oxygen gas at 700-900° C.to produce carbon monoxide and hydrogen.